My own experience was an isolated occasion, and I was the beneficiary of countless other upgrades from GF which were fully honoured, so no complaints from me.

But the case of that couple at BKK is quite different, and it's a near certainty that they would (understandably) not only have felt rather miffed at the time, but would also have subsequently related the incident many times to friends and relatives ; and word of mouth can of course have just as much negative impact as positive.......